Dyeing leather: exhaustion process using combination of pigment dispersion and aqueous solution of water-soluble sulfur dye

Abstract

The process for dyeing leather by the exhaust method comprises allowing a pigment dispersion and an aqueous solution of sulfur dye to act on the conventionally pretreated leather in one step or in succession. It affords a high depth of shade and a high brilliance which are not achieved by using the pigment or the sulfur dye on its own.

What is claimed is: 
     
       1. A process for dyeing leather by the exhaust method, which comprises allowing a pigment dispersion consisting essentially of a pigment, a dispersant and water and an aqueous solution of sulfur dye to act on the leather in one step or in succession. 
     
     
       2. The process as claimed in claim 1 wherein a pigment dispersion comprising the following composition is allowed to act on the leather: 10 to 60% by weight of pigment, 2 to 30% by weight of dispersant, 0 to 30% by weight of solvent, 0 to 5% by weight of preservative and 30 to 70% of water. 
     
     
       3. The process as claimed in claim 1 wherein an aqueous solution of sulfur dye is allowed to act on the leather, said solution of sulfur dye containing, based on the shaved weight of the leather, 20 to 400% by weight of water, 0.5 to 8% by weight of sulfur dye and, optionally, 0.1 to 6% by weight of pigment dispersion and/or 0.1 to 6% by weight of another water-soluble dye. 
     
     
       4. The process as claimed in claim 1 wherein the dyeing time is 20 to 300 minutes. 
     
     
       5. The process as claimed in claim 2 wherein said composition comprises: 20 to 40% by weight of pigment,   4 to 12% by weight of dispersant,   5 to 12% by weight of solvent,   
     
     
       0. 1 to 1% by weight of preservative, and 35 to 55% by weight of water.   
     
     
       6. The process as claimed in claim 1 wherein an aqueous solution of sulfur dye is allowed to act on the leather, said solution of sulfur dye containing, based on the shaved weight of the leather, 20 to 400% by weight of water, 0.5 to 8% by weight of sulfur dye and, optionally, 0.1 to 6% by weight of pigment dispersion and/or 0.1 to 6% by weight of another water-soluble dye. 
     
     
       7. The process as claimed in claim 3 wherein said aqueous solution of sulfur dye contains, based on the shaved weight of the leather, 50 to 200% by weight of water,   1.5 to 6% by weight of sulfur dye, and, optionally,   0.1 to 3% by weight of pigment dispersion and/or   0.1 to 4% by weight of another water-soluble dye.   
     
     
       8. The process as claimed in claim 1 wherein the dyeing time is 30 to 120 minutes. 
     
     
       9. The process as claimed in claim 6 wherein said aqueous solution of sulfur dye contains, based on the shaved weight of the leather, 50 to 200% by weight of water,   1.5 to 6% by weight of sulfur dye, and, optionally,   0.1 to 3% by weight of pigment dispersion and/or   0.1 to 4% by weight of another water-soluble dye.   
     
     
       10. The process as claimed in claim 2, wherein the dyeing time is 30 to 120 minutes. 
     
     
       11. The process as claimed in claim 3, wherein the dyeing time is 30 to 120 minutes. 
     
     
       12. The process as claimed in claim 6, wherein the dyeing time is 30 to 120 minutes. 
     
     
       13. A process for dyeing leather by the exhaust method, which comprises allowing a pigment dispersion comprising 10 to 60% by weight of pigment, 2 to 30% by weight of dispersant, 0 to 30% by weight of solvent, 0 to 5% by weight of preservative, and 30 to 70% by weight of water, and an aqueous solution of sulfur dye containing, based on the shaved weight of the leather, 20 to 400% by weight of water and 0.5 to 8% by weight of sulfur dye, to act on the leather in one step or in succession.   
     
     
       14. A process according to claim 13, wherein said aqueous solution further comprises 0.1 to 6% by weight of pigment dispersion and/or 0.1 to 6% by weight of another water-soluble dye. 
     
     
       15. A process for dyeing leather by the exhaust method, which comprises allowing a pigment dispersion consisting essentially of a pigment, a dispersant and water and an aqueous solution of sulfur dye to act on the leather in succession.